CVE-2026-59924

Summary

A path traversal issue exists in mistune's Include directive when markdown files are processed using md.read(). A crafted include path can cause files outside the intended markdown directory to be accessed.

Details

The issue occurs in the Include.parse() method where user-supplied paths are joined and normalized without verifying that the resulting path remains within an expected directory.

relpath = self.parse_title(m)
dest = os.path.join(os.path.dirname(source_file), relpath)
dest = os.path.normpath(dest)

Because the final path is not restricted to a trusted base directory, path traversal sequences such as ../ may reference files outside the intended location.

Proof of Concept

Create a markdown file:

.. include:: ../../../example.txt

Process it using:

import mistune
from mistune.directives import RSTDirective, Include

md = mistune.create_markdown(
    plugins=[RSTDirective([Include()])]
)

result, state = md.read("test.md")
print(result)

Impact

Applications that process untrusted markdown files with the Include directive enabled may allow unintended file access. The impact depends on how the feature is used and what files are accessible to the running process.

Recommended Fix

Validate the resolved path and ensure it remains within an allowed directory before opening the file.

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, Include.parse() joins and normalizes user-supplied include paths without verifying that the result remains within the intended markdown directory, allowing crafted include paths to access files outside that directory when markdown files are processed using md.read(). This issue is fixed in version 3.3.0.

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, Include.parse() joins and normalizes user-supplied include paths without verifying that the result remains within the intended markdown directory, allowing crafted include paths to access files outside that directory when markdown files are processed using md.read(). This issue is fixed in version 3.3.0.

This update for python-mistune fixes the following issues

• CVE-2026-59922: quadratic-time parsing on long runs of some markers in formatting.py can lead to DoS (bsc#1271117).
• CVE-2026-59923: HTMLRenderer.safe_url() does not block percent-encoded javascript URIs and allows for XSS (bsc#1271119).
• CVE-2026-59924: improper processing of user-supplied include paths in Include.parse() can lead to path traversal and arbitrary file reads (bsc#1271121).
• CVE-2026-59925: quadratic-time parsing on long runs of some emphasis pairs in inline_parser can lead to DoS (bsc#1271125).
• CVE-2026-59926: improper escaping in render_admonition() can lead to atribute injection and XSS (bsc#1271127).
• CVE-2026-59927: uncontrolled recursion when processing two markdown files that include each other can lead to a DoS (bsc#1271128).
• CVE-2026-59928: quadratic-time parsing on long lists of repeated reference-link definitions in block_parser can lead to DoS (bsc#1271131).
• CVE-2026-59929: HARMFUL_PROTOCOLS list misses legacy and chained schemes and allow arbitrary script execution in user agents (bsc#1271132).
• CVE-2026-59930: the toc plugin and TableOfContents directive generate heading IDs with predictable values and allow for collisions with attacker-controlled id="toc_N" content (bsc#1271082).

This update for python-mistune fixes the following issues

• CVE-2026-59922: quadratic-time parsing on long runs of some markers in formatting.py can lead to DoS (bsc#1271117).
• CVE-2026-59923: HTMLRenderer.safe_url() does not block percent-encoded javascript URIs and allows for XSS (bsc#1271119).
• CVE-2026-59924: improper processing of user-supplied include paths in Include.parse() can lead to path traversal and arbitrary file reads (bsc#1271121).
• CVE-2026-59925: quadratic-time parsing on long runs of some emphasis pairs in inline_parser can lead to DoS (bsc#1271125).
• CVE-2026-59926: improper escaping in render_admonition() can lead to atribute injection and XSS (bsc#1271127).
• CVE-2026-59927: uncontrolled recursion when processing two markdown files that include each other can lead to a DoS (bsc#1271128).
• CVE-2026-59928: quadratic-time parsing on long lists of repeated reference-link definitions in block_parser can lead to DoS (bsc#1271131).
• CVE-2026-59929: HARMFUL_PROTOCOLS list misses legacy and chained schemes and allow arbitrary script execution in user agents (bsc#1271132).
• CVE-2026-59930: the toc plugin and TableOfContents directive generate heading IDs with predictable values and allow for collisions with attacker-controlled id="toc_N" content (bsc#1271082).